The invention relates to an x-ray grid and cassette-mounting arrangement for x-ray examination apparatus comprising rails for a cassette receiving tray and also comprising a mobile stray radiation absorbing grid or grating known as a Bucky diaphragm or a Potter-Bucky grid, together with a motor drive and mounting therefor.
In the case of most x-ray examination apparatus in which the patient can be examined while reclined on a horizontal, more or less tilted, patient support platform or while standing against a support wall, there is disposed in the radiation direction, directly beneath the patient support platform, or directly behind the support wall, respectively, a guide for a cassette plate or tray. In order to obtain x-ray photographs with good detail-recognizability, it is generally known to provide, in the present instance, a motor-driven stray radiation grating or grid between the patient support platform, or the support wall, respectively, and the x-ray film cassette. The motor-driven back and forth movement of the stray radiation grating or grid here prevents an image from being formed of the latter on the x-ray photograph. Nevertheless, the grating absorbs the obliquely directed stray rays which reduce the contrast, and thus improves the photographic quality. Moreover, it is of decisive significance in terms of the photographic quality that the x-ray film and the stray radiation grating be arranged as closely as possible behind the examination subject. Such units comprising a cassette plate or tray, a stray radiation grating, and the respective drive, are offered on the market in the form known in Germany as "catapult raster" cases. Such cases or assemblies are installed with the smallest possible distance beneath the patient support in the case of a reclining patient, or behind the support wall in the case of a standing patient.
In the case of the known assemblies of this type, the stray radiation grating, designed for a specific film-to-focus-distance, rests in a plate metal frame which is moved back and forth by means of a motor in the housing of the assembly. In the case of such assemblies, which are inserted behind support walls and in which, on occasion, operation is carried out with a different film to focus distance, the stray radiation grating can be replaced by another stray radiation grating designed for the different film to focus distance to be utilized.